The present invention relates to an ophthalmic surgery apparatus for performing treatment by irradiating a treatment laser beam to a subject""s eye, and more particularly to a mechanism for aligning the irradiation optical axis of a laser irradiating optical system for applying a treatment laser beam, with a patient""s eye, and also to a laser irradiation controlling mechanism associated with the alignment.
As an ophthalmic surgery apparatus for performing treatment by irradiating a laser beam for treatment to a patient""s eye, a corneal surgery apparatus using an excimer laser beam, for example, is known. This apparatus is used for refractive correction by changing the curvature of the cornea with an excimer laser beam irradiated to the corneal surface.
In this apparatus, the patient is caused to gaze at a fixation target to fix the position of the patient""s eyeball, and the irradiation optical axis of the laser irradiating optical system and the patient""s eye are brought into alignment in a desired state by using an alignment target or the like. After completion of the alignment, a part of the cornea is ablated at a set amount within an intended area.
As disclosed in U.S. Pat. No. 6,159,202, a corneal surgery apparatus (ophthalmic surgery apparatus) having an automatic tracking mechanism has also been proposed. This apparatus has a function of moving the irradiation optical axis of the laser irradiating optical system to follow (track) the movement of the patient""s eyeball. This apparatus makes it possible to prevent the cornea from being ablated in an unplanned shape as the operator continues the laser irradiation without becoming aware of the movement of the patient""s eyeball during the laser irradiation. With this tracking mechanism, an image of an anterior portion of the patient""s eye is constantly obtained by a CCD camera or the like during the laser irradiation. Then, if it is detected on the basis of the obtained image that the detected position of the pupillary center is moved out of a predetermined first allowable range from a reference position, such as irradiation optical axis, (e.g., out of a range of 0.005 mm in radius from the reference position), the irradiation optical axis is subjected to tracking so that the position of the pupillary center and the reference position will be aligned with each other on the basis of the obtained image. In addition, the laser irradiation is discontinued if the position of the pupillary center is moved out of a predetermined second allowable range, such as the imaging range of the camera, the movable range of the irradiation optical axis, and a range offset largely from the reference position (e.g., a range of 1 mm in radius from the reference position).
However, the processing speed associated with image capture by the camera and image process is low as compared to the speed of the eyeball movement. For this reason, the automatic tracking in the related art has a slight time lag until the irradiation optical axis is subjected to tracking or the laser irradiation is discontinued after the patient""s eye is moved. Particularly, in a case where the laser irradiation is discontinued, an unexpected portion may be ablated during the time lag until the discontinuance.
In view of the above-described problems of the related art, an object of the invention is to provide an ophthalmic surgery apparatus capable of performing accurate treatment by ensuring appropriate alignment between the irradiation optical axis of the laser irradiating optical system and the patient""s eye.
(1) An ophthalmic surgery apparatus by which treatment laser beam is irradiated onto a desired portion of a patient""s eye and for treatment of the portion, the apparatus comprising:
a laser irradiating unit having a laser beam source which emits the treatment laser beam, and an irradiating optical system which optically guides the treatment laser beam emitted from the laser beam source onto the portion;
an ocular movement detecting unit which detects a potential difference between a cornea and a retina, and detects an ocular movement of the patient""s eye based on the detected potential difference; and
an irradiation controlling unit which controls the irradiating unit based on a result of detection by the detecting unit.
(2) The apparatus of (1), wherein the detecting unit includes a plurality of electrodes to be attached to a periphery around the patient""s eye.
(3) The apparatus of (2), wherein the electrodes includes a pair of electrodes to be attached to the periphery around the patient""s eye and located in at least one of vertical and horizontal directions.
(4) The apparatus of (1), wherein irradiation controlling unit controls the irradiating unit so that the laser irradiation is discontinued if the detecting unit detects a potential difference not smaller than or not larger than a predetermined threshold value.
(5) The apparatus of (1), further comprising:
a setting unit which variably sets the threshold value based on inputted data of the patient""s eye.
(6) The apparatus of (1), further comprising:
a moving unit which relatively moves an irradiation optical axis of the irradiating optical system with respect to the patient""s eye; and
a movement controlling unit which controls the moving unit based on a result of detection by the detecting unit.
(7) The apparatus of (6), further comprising:
a signal generating unit which generates a tracking signal for tracking the movement of the patient""s eye if the detection unit detects a potential difference not smaller than or not larger than a predetermined threshold value, and
wherein the movement controlling unit controls the moving unit based on the tracking signal.
(8) The apparatus of (1), wherein:
the apparatus includes a corneal surgery apparatus; and
the laser beam source emits excimer laser beam as the treatment laser.
(9) An ophthalmic surgery apparatus by which treatment laser beam is irradiated onto a desired portion of a patient""s eye and for treatment of the portion, the apparatus comprising:
a laser irradiating unit having a laser beam source which emits the treatment laser beam, and an irradiating optical system which optically guides the treatment laser beam emitted from the laser beam source onto the portion;
an ocular movement detecting unit which detects a potential difference between a cornea and a retina, and detects an ocular movement of the patient""s eye based on the detected potential difference;
a moving unit which relatively moves an irradiation optical axis of the irradiating optical system with respect to the patient""s eye; and
a movement controlling unit which controls the moving unit based on a result of detection by the detecting unit.
(10) The apparatus of (9), further comprising:
a signal generating unit which generates a tracking signal for tracking the movement of the patient""s eye if the detection unit detects a potential difference not smaller than or not larger than a predetermined threshold value, and
wherein the movement controlling unit controls the moving unit based on the tracking signal.
The present disclosure relates to the subject matter contained in Japanese patent application No. 2000-98411 (filed on Mar. 31, 2000), which is expressly incorporated herein by reference in its entirety.